Process of producing flame-resistant molded articles from epoxy resins



United States Patent Hermann Richtzenhain, Cologne-Sulz, Germany, as-

signors to Dynamit Nobel Aktiengesellschaft, Troisdorf, Bezirk Cologne, Germany, a corporation of Germany No Drawing. Filed Nov. 23, 1965, Ser. No. 509,433 Claims priority, application Germany, Nov. 24, 1964, D 45,906 21 Claims. (Cl. 260-47) This invention relates to the hardening of epoxy resins. It more particularly relates to hardened epoxy resins which are substantially flame-resistant.

The manufacture of epoxy resin compounds having flame-resistant properties isin the prior art. Flame-resistance is the technically valuable ability of a synthetic resin which has been ignited by a flame to extinguish itself promptly instead of continuing to burn indefinitely and constantly. Flame-resistant properties can be achieved, for example, by the use of hardeners containing chlorine or bromine, such as dichloromaleic acid anhydride or tetrachlorophthalic acid anhydride. The use of epoxy resins containing chlorine or bromine, such as the diglycidyl ether of tetrachloro or tetrabromo diphenylol propane, also results in products with flame-resistant 1 properties. Another possibility consists in the use of additives which contain chlorine, bromine and/or phosphorous, such as triphenyl phosphite or tri-B-chloroethyl phosphate. Flame-resistant compounds on a basis of components containing chlorine or bromine require a relatively high chlorine or bromine .content. This high halogene content, however, frequently results in considerable technical disadvantages. For example, an epoxy resin made from tetrachloro or tetrabromo diphenylolpropane and epichlorhydn'n has a high viscosity and is therefore substantially more difficult to work with than the corresponding resin made of halogen-free diphenylolpropane. Another possibility for the manufacture of flame-resistant compounds is the use of epoxy resins containing phosphorous and made, for example, by the reaction of epoxies containing hydroxyl groups with the halides of phosphoric, phosphonic, or phosphinic acids, or by the reaction of epi-ha-lohydrines with dialkylphosphites. Another known method is the use of phosphoric acid, phosphoric acid esters, tertiaryphosphites and phosphonic acids as hardeners for epoxy resins. The mechanical characteristics of the compounds obtained with these hardeners do not, however, meet the necessary requirements, especially on account of their great brittleness.

In co-pending application Ser. No. 472,311 there is disclosed a method for preparing flame-resistant epoxy resin materials and of hardened products therefrom. These products are the reaction products of various known or common epoxy resins and aromatic phosphorins. As set forth in said parent application, the aromatic phosphorins are exemplified by the reaction products of trivalent and polyvalent phosphorous compounds and aromatic hydroxy carboxylic acids. These reaction products are mixed ester anhydrides. These mixed ester anhydrides contain the group wherein the Zs are aryl radicals having among their ring Patented Apr. 16, 1968 carbon atoms the 5 and 6 position carbon atoms of the phosphorous-containing rings.

Compounds of this kind can be for example described by the following general formulas, for example:

wherein R may be chlorine or bromine, R and R may be each hydrogene, alkyl, alkoxy halogene or a condensed ring.

These compounds can be obtained by known processes, as for example by the transposition of aromatic ohydroxycarboxylic acids (which may be further substituted if desired) with phosphorus trichloride, dichlorophosphorous acid esters, dichlorophosphoric acid esters, and dichlorophosphinic and dichlorophosphonic acids.

Of the aromatic o-hydroxyoarboxlic acid, salicylic acid is especially suitable, as well as its substitution products, such as the monochloro or dichloro or monobromo or dibromo salicylic acids, and the o-hydroxynaphthalene carboxylic acids corresponding thereto.

By the reaction of these acid components and the previously described phosphorus compounds, the following compounds, for example, are obtained: 2-chloro-4-oxo- 5,6-benzo-1,3,2-dioxaphosphorin, 2 bromo 4 oxo-5,6- benzo-1,3,2-dioxaphosphorin, 2,4 dioxo 2 chloro-5,6- benzo-1,3,2-dioxaphosphorin, 2,4 dioxo 2 bromo-5,6- benZo-1,3,2-dioxaphosphorin.

It is an object of this invention to produce molded articles and coatings by hardening flame-resistant epoxy resins.

It is another object of this invention to prepare flameresistant epoxy resins containing phosphorus constituents as the flame retardants.

It is a further object of this invention to prepare flameretardant epoxy resins in a novel manner.

Other and additional objects of this invention will appear from a consideration of the whole of this specification and the claims appended hereto.

In accord with, and fulfilling these objects, one facet of this invention resides in the reaction of a phosphorin of the formula R, R and R having the previously described meaning, with a polyepoxide-containing aliphatic, cycloaliphatic or aromatic compound under such conditions, including a temperature of about 0 up to C. that soluble 15- ,halogenated aliphatic, cycloaliphatic or aromatic phosphoric or phosphorus acid esters result and, thereafter, in a second stage hardening the resin formed to produce molded articles and coatings by increasing the temperature to above 80 C. and preferably to a temperature within the range of about 80-200 C., most preferably l50 C.

The hardening of these reaction products to produce molded articles and coatings in the second stage of the process can take place at temperatures above 80 C. without any further addition of hardener, or possibly in the presence of hardening accelerators, by the reaction of the cyclic anhydride group with the epoxy groups present. However, hardening may also be carried out, in order to obtain particular mechanical properties, by the addition of other common hardening agents, such as carbonic acid anhydrides or polyols, or hardening accelerators, especially in the case of an excess of epoxy groups, in a temperature range of 80150 C.

Thus, for example, in accordance with the invention, a polyepoxide such as a diglycidyl ether of 2,2-bis-(4- hydroxy-phenyl)-propane is reacted in a first stage with 2-chloro-4-oxo-5,6-benzo-1,3,2-dioxaphosphorin to produce a soluble product. In the reaction, the phosphorus acid halide enters into reaction with an epoxy group of the polyepoxide, by ring opening of an expoxy ring to form a 'betachloroalkylphosphorous acid group by sustaining the cyclic mixed anhydride structure. Thus, in the instant illustration, one mole of a bifunctional epoxy compound like the diglycidyl ether of 2,2-bis-(4-hydroxyphenyl)-propane is reacted with one mol of 2-chloro-4- oxo-5,6-benzo-1,3,2-dioxaphosphorin to form a compound which contains not only a hardenable epoxy group but also an anhydride group as a hardening group. The molar ratio of the reaction can also be chosen, however, in such a manner that the epoxy groups, with respect to the anhydride groups, are present either in slight or great excess. The phosphorus-containing mixed ester anhydride of an aromatic ortho-hydroxy carboxylic acid may be used in a molar ratio to the epoxy compound of 1 to greater than 1, preferably 1 to 2. The given molar ratio is applied in the case of a diepoxide compound. Epoxide compounds with more than two epoxy groups are used in such an amount, that the relation of the epoxy group to the phosphorus-containing compound is the same, that means, more than two epoxy groups per mixed ester anhydride are used. By blending previously formed epoxy anhydride adducts with polyepoxides, similar results may be obtained. The reaction gives hardenable products which are soluble in organic solvents and have a stable viscosity. Thereafter, in a second stage, the reaction product is hardened at a temperature above 80 C. possibly under addition of a known epoxy resin, carbonic acid anhydride or polyol hardener or known hardening accelerator.

While the above is given as illustrative of the reaction and the reaction product, according to the invention it will be apparent that the same reaction will take place if the diglycidyl ether of 2,2-bis-(4-hydroxyphenyl)- propane is replaced by another epoxy compound contaim ing two or more epoxy groups in the molecule.

Particularly suitable are the polyepoxies of polyunsaturated hydrocarbons (vinylcyclohexene, dicyclopentadiene, cyclohexadiene, cycl-ododecatriene, butadiene, polybutadiene, divinylbenzenes), oligomers of epichlorhydrin and the like, epoxy ethers of polyvalent alcohols (ethylene glycols, propylene glycols and butylene glycols, polyglycols, thiodiglycols, glycerine, pentaerythritol, sorbitol, polyvinyl alcohol, polyallyl alcohol, etc.), epoxy ethers of polyvalent phenols (resorcinol, hydroquinone, bis-(4-oxyphenyD methane, bis-(4-oxy S-methylphenyD-methane, bis-(4-oxy-3,5-dichlorop'henyl) methane, bis-(4-oxy-3,5-dibromophenyl)-methane, bis-(4-oxy-3,5 difiuorophenyD- methane, 1, 1-bis-(4-oxypheny1) ethane, 2,2-bis-(4-oxyphenyD-propane, 2,2-bis-(4-oxy-3-methylphenyl) propane, 2,-2-bis-(4-oxy-5-chlorophenyl)-propane, 2,2-bis-(4- oxy 3,5-dichlorophenyl) propane, bis (4-.oxyphenyl)- phenylmethane, bis-(4-oxyphenyl)-diphenylmethane, bis- 4-oxyphenyl)-4' methylphenylmethane, 1,1-bis-(4 oxyphenyl)-2,2,2-trichloroethane, bis-(4-oxyphenyl)-4-(chlorophenyl) -met-hane, 1,'1-bis-(4-oxyphenyl) -cyclohexane, bis-(4-oxyphenyl)-cyclohexylmethane, 4,4'-diovydiphenyl, 2,2'-dioxydiphenyl, 4,4-dioxydiphenylsulfone and the oxyethylethers and phenolformaldehyde condensation products thereof), and also polyepoxy compounds which have been made by prior art methods from poly-unsaturated carboxylic acids or monounsaturated carboxylic acid esters of unsaturated alcohols, glycidyl esters of polybasic carboxylic acids, polyglycidyl esters which can be obtained by polymerization or copolymerization of glycidyl esters 4 of unsaturated acids, or of other acid compounds (cyanuric acid and cyclic trimethylenetrisulfone or their derivatives, etc.).

In addition to the epoxy compounds with 2 and more epoxy groups cited by way of examples, mixtures of the same with monoepoxies can be used for the manufacture of the flame-resistant compounds. For example, the monoepoxies of the following types of compounds can be used: mono-unsaturated hydrocarbons (ethylene, propylene, butylene, cyclohexene, styrene), halogenous epoxies (epichlorhydrin), epoxy ethers of univalent alcohols (methyl, ethyl, butyl, Z-methylhexyl and dodecyl alcohol, etc.), epoxy ethers of univalent phenols (phenol, cresol and other phenols substituted in the ortho or para position), glycidyl esters of unsaturated carboxylic acids, epoxidized esters of unsaturated alcohols or unsaturated carboxylic acids, and the acetals of glycidaldehyde.

Similarly, the main chloro-substituted phosphorin could be replaced by a Z-substituted phosphorin to result in a phosphorinic acid derivative of a bromo-substituted phosphorine.g., 2-bromophosphorin. Further, 2-chloroor bromo-substituted phosphorin can have many other substituents as, for instance, hydrogene, alkyl or alkoxy groups of varying size substituted on the benzo-substituent or it can be substituted with other fused phenyl ring on the benzo-substituent.

The preparation of the epoxide-anhydride adduct in the first stage of the process takes place suit-ably at as low a temperature as possible in order to prevent any premature reaction between the anhydride and the epoxy groups.

The reaction product formed in the first stage is substantially a 1:1 adduct of a halo phosphorus and an epoxide group.

It is, of course, to be understood that mixed reactants can be used in this invention, whereupon mixed products will be made.

The first stage epoxy halo-phosphorin adducts in accordance with the invention are readily soluble in many organic solvents, e.g., triethyleneglycol, and have stable viscosities. Further, reaction through the anhydride group of the phosphorin portion of the adduct with epoxy resins takes place at relatively high temperatures -200 C. and preferably about C., to produce the hardened flame-retardant epoxy resin molded articles and coatings.

The hardening reaction suitably takes advantages of accelerators such as phenols: particularly, dialkyl-aminoalkyl phenols (4-(dimethylaminomethyl)-phenol, 2,4,6- tris-(dimethylaminomethyl)-phenol), Lewis acids, (ZnCl- SnCl BF B F complex compounds and such), phosphines, arsines, stibines and others generally known epoxy resin hardening accelerators.

If such additional hardeners are employed, it has been found desirable to mix the phosphorin adduct with the additional hardener at moderate temperatures and thereafter to heat the mixture to above 80 C. to carry out the hardening reaction. Additional hardeners are carbonicacid anhydrides and polyols.

The carbonic acid anhydrides suitable for use in the invention include cyclic acid anhydrides of aliphatic, aromatic, and heterocyclic carboxylic acids. In addition, the products conventionally used as hardening anhydrides, such as for instance, maleic, or succinic acid anhydride, Z-dodecenylsuccinic acid anhydride, phthalic acid anhydride, tetraand hexahydrophthalic acid anhydride, trimellithic and pyromellithic acid anhydride, itaconic acid anhydride, hexachloroendomethylenetetrahydrophthalic acid anhydride as well as their substitution products and the diene addition products of unsaturated acids and dienes are particularly well suited for use in the reaction with the epoxy compounds especially in the reaction with polyepoxides as carried out in accordance with the invention.

Suitable polyols are ethylene glycol, propylene glycol, butylene glycol, hexanediols, higher glycols which can be obtained, for example, by the hydrogenation of dicarboxylic acids; xylene glycol, hexahydroxylene glycol, 1,4-cyclohexanediol, glycerol, diglycerol, triglycerol, and higher polyglycerol, methyl glycerol, trimethylolethane,

tinned for 2 hours. After removing the benzene in vacuum, a viscous epoxide-anhydride adduct was obtained.

200 g. of this epoxide-anhydride adduct were, in the presence of 0.5 g. ZnCl dissolved in 1 g. of triethylene trimethylolpropane, pentaerythritol, dipentaerythritol, 5 glycol, and hardened at 150 C. in 60 minutes to form pentitols, hexitols, and mono-, di and polysaccharides, a solid synthetic resin block which showed flame-resistant which may be partially etherified or esterified. Polyglyproperties. cols which are produced, for example, by the polymer- Exam 1e 8 ization or copolymerization of olefin oxides and which p can include both low-molecular products, such as diethyl- The use of equivalent amount of ene glycol, triet-hylene glycol, and the like, as w ll a benzo-1,3,2-d1oxaphosphorin under the same conditions as higher molecular products are also included in this group. dfiscribed E p 1 g a Solid Synthetic resin Additionally polyvinyl alcohol, partially acylated polynlsh Wlth slmllaf p p vinyl alcohol and polyallyl alcohol, as well as the co- Example 9 polymers of allyl alcohol with other unsaturated cOmpounds o Partially or completely Saponified polymers of The use of an equivalent amount of a diglycidyl ether vinylidene carbonate can be employed in the reaction of 14'butanedw1 Wlth an epoxy value of 100 with epoxides in accordance with the invention. of Fpoxy compound gave under h copdlnons If desired, the hardened epoxy resin product can be scribed m Example 7 a Shaped body with sunllar Prop treated at about 30-50 C. above the hardening tempera- 20 ewes ture for after-hardening it and thus improve its me- Example 10 chanical properties. The use of an equivalent amount of resorcinol diglycid- The following examples serve to illustrate the invenylether with an epoxy value of 0.76 per 100 grs. of epoxy tion but are in nowise to be construed as limitative therecompound gave under the conditions described in Examof: ple 7 a shaped body with similar properties.

Example 1 Example 11 270 6'benZ'1'3z'dioxaphosphorin The use of an equivalent amount of 4-vinylcyclohexenewh1h had been brought to were added dioxide gave under the conditions described in Example dropwise, while stirring, at room temperature (22 C.) 7 ashaped body with similar properties within two hours to 1000 g. of a diglycidyl ether of 2,2- We claim: bis'(4'hydmxypher lyl)'pmpfme i g an ePoxide f 1. The process of production of molded articles and of 053/100 g. resin. Reaction set in immediately with a coatings by hardaning flame mtardant resins which strong fiewjlopment of heatreactfon temperatufe prises reacting an epoxy compound having at least 2 1,2- s {namtameq by f durmg the dropwlse epoxy groups per molecule with a mixed ester anhydride reaction and stirring was continued at the sametemperaf an aromatic orthmlwdroxy b li id f h f rture for 2 hours. After completion of the reaction, ionomula genic chlorine could no longer be detected by means of O O O hydrolysis. A liquid epoxide-anhydride adduct, soluble in organic solvents and stable in its viscosity was obtained. R r R 1 200 g. of this epoxide-anhydride adduct were dissolved R3 L 0 R3 L in l g. triethylene glycol in the presence of 0.5 g. ZnCl C and hardened at 150 C. for 60 minutes to form a solid H g synthetic resin varnish. The product has a Vicat value of 0 105 C. and exhibited flame-resistant properties. or mixtures of such wherein R is chlorine or bromine, R Examples and R is each hydrogen, alkyl, alkoxy, halogcne or a condensed ring at a temperature of from 0 up to 80 C. An epoxide anhydride adduct was P pared according and thereafter hardening the resin thus produced by heatto Example 1 from 1000 g. of diglycidyl ether of 2,2- ing the same to a temperature of from 80200 C. bis-(4-hydroxyphenyl)-propane with an epoxide content 2. Process according to claim 1 wherein'said mixed esof 053/100 g. of resin and 135 g. of 2-chloro-4-oxoter anhydride of an aromatic ortho-hydroxy carboxylic 5,6-benzo-1,3,2-dioxaphosphorin, and the following hardacid is used in a molar ratio to said epoxy compound ening runs were carried out with it under the hardening of 1 to greater than 1, preferably 1 to 2. conditions described. 3. Process according to claim 2 wherein said hardening The following table shows the values obtained for the is carried out at a temperature of from 100150 C. mechanical properties which were determined on test 4. Process according to claim 2 wherein said mixed esarticles as prepared above. Hardening was carried out at ter anhydride is 2-chloro-2,4-dioxo-5,6-benzo-1,3,2-dioxa- 130 C. and accelerated with 0.5 wt. percent of ZnCl phosphorin.

dd. 1. .1 anna 2.232% ay t /ins Example 23333385) A mm! M wmg') $111. (k /511. k (511. (cm. kgJemfl) 0 200 40 562 1,292 10.2 1224/1179 116 200 1,1,1-trimethylolpropane (1a) 417 936 6.4 1273/1224 105 200 2, 2-dimethylolbutanoL3 (15 60 423 950 7. 2 1178/1152 93 200 Hexahydrophthalic acid anhydride (35), 35 430 1, 038 12. 0 1370/1315 135 200 Chlorophthalic acid anhydride 45 40 416 1,115 11.5 1384/1326 1741 Example 7 5. Process according to claim 2 wherein said mixed 292 g. of 2-chloro-2,4-dioxo-5,6-benzo-1,3,2-dioxaphosgi gg iff f 2 phorin fi f fi in 400 of benzene were added P 6. Process according to claim 2 wherein said mixed wise whlle stlmng at room temperature C) Wlth ester anhydride is 2-bromo-2,4-dioxo-5,6-benzo-1,3,2-diin two hours to 1000 g. of a diglycidyl ether of 2,2-bisoxaphosphorm y yp nyD-p p having an epoxide Value of 7. Process according to claim 2 wherein said mixed 0.53/ 100 g. resin. The reaction temperature was mainester anhydride is 2-bromo-4-oxo-5,6-benzo-l,3,2-dioxatained here under 40 C. and stirring was hereafter conphosphorin.

8. Process according to claim 2 wherein the epoxy com pound is a polyglycidyl ether of a polyvalent phenolic compound.

9. Process according to claim 8 wherein the epoxy compound is a diglycidyl ether of 2,2-bis-(4-hydroxyphenyl)- propane.

10. Process according to claim 8 wherein the epoxy compound is a diglycidyl ether of resorcinol.

11. Process according to claim 8 wherein the epoxy compound is a diglycidyl ether of hydroquinone.

12. Process according to claim 2 wherein said mixed ester anhydride is Z-chloro-4-oxo-5,6-benzo-1,3,2-dioxaphosphorin and said epoxy compound is a diglycidyl ether of 2,2-bis-(4-hydroxyphenyl)-propane.

13. Process according to claim 2 wherein said hardening is eifetced in the presence of an accelerator.

14. Process according to claim 13 wherein said-accelerator is a Lewis acid.

15. Process according to claim 14 wherein said Lewis acid is ZnCl 16. Process according to claim 2 wherein said hardening is effected in the presence of a polycarboxylic acid anhydride as a hardening agent.

17. Process according to claim 2 wherein said hardening is effected in the presence of a polyol as a hardening agent.

18. Process according to claim 17 wherein said polyol is 1,1,1-trimethylol-propane.

19. Process according to claim 17 wherein said polyol is 2,2-dimethylol-butanol-3. 1

20. Process according to claim 16 wherein the polycarboxylic acid anhydride is hexahydrophthalic acid anhydride.

21. Process according to claim 16 whereinvthepolycarboxylic anhydride is chlorophthalic acid anhydride.

References Cited UNITED STATES PATENTS 3,245,940 4/1966 Ronay et a1 26047 20 WILLIAM H. SHORT, Primary Examiner.

T. D. KERWIN, Assistant Examiner. 

1. THE PROCESS OF PRODUCTION OF MOLDED ARTICLES AND COATING BY HARDENING FLAME RETARDANT RESINS WHICH COMPRISES REACTING AN EPOXY COMPOUND HAVING AT LEAST 2 1,2EPOXY GROUPS PER MOLECULE WITH A MIXED ESTER ANHYDRIDE OF AN AROMATIC ORTHO-HYDROXY CARBOXYLIC ACID OF THE FORMULA 